U.S. Patent Application Publication No. 2004/0155347 A1 (Ho et al.) addresses the problem of vertically routing a conductive rod from the bottom of a substrate, thorough all layers, to the top of the substrate. With the aid of the presented embodiment an increase in routing density can be achieved. Nevertheless, when utilizing this method in microcircuits having for example hundreds of pads, it is inefficient and slow thus increasing manufacturing time and costs.
U.S. Patent Application Publication No. 2002/0135058 A1 (Asahi et al.) discloses a component build-in module with plated through hole solutions. With the aid of the presented embodiment an increase in routing density can be achieved as well as build-up layers need not to be constructed so many or at all. Nevertheless, when utilizing this method in microcircuits having for example hundreds of pads, it is inefficient and slow thus increasing manufacturing time and costs.
Presently, there are many different methods and available technologies to make an electrical connection between two sides of a wiring board with the aid of a penetrated hole, also called a through hole. One early phase method to make a through hole is to use a conductive rivet pin that is assembled into a through hole of an otherwise ready-made wiring board. The rivet pin solution is slow to assemble as well as expensive, unreliable and does not adequately reduce the size of necessary through holes. Other prior art methods are plated through holes (PTH) and via-on-via structures. All of the prior art methods fail to solve the problems presented above.
For example, by using chemical and/or electroplating technologies it is practically impossible to achieve reliable conductive micro vias having aspect ratio (height/width) greater than 1,00 when the diameter of micro vias are 150 μm or less. The same applies in case of through holes where a typical aspect ratio is 8:1 and in maximum 12:1. In other words, the throwing power limits the narrow and deep through holes or micro vias becoming reliably conductive and solid with the conductive material. Throwing power means ability to saturate narrow and deep through holes or micro vias with conductive material by means of chemical or electrolytic growing methods. The situation is also likewise by using any kind of conductive paste or adhesive in micro vias and through holes having a respective aspect ratio greater than mentioned above when the diameter of micro vias and through holes are 150 μm or less.
Thus, the background art contains different solutions that do not adequately provide high routing efficiency with an affordable price of the product. There remains a need to seek further techniques with potentially improved properties in view of routing efficiency and price, in particular when it is aimed to increase the number of contacts of the components and narrow the pitch between the contact lands, or bumps, on the component.